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Please, just assume that the case below is how it is and I must solve it with what I have. Or at least understand what is wrong.

Two identical computers connected between them with 10G cable. Both computers run Windows 8.1 Pro. Computer "A" streams video over tcp and computer "B" reads it. The streamer has a log window that reports if frames are being dropped. Both streamer and reader applications are third-party and I don't have their source code. Everything works fine. But, when I replace "B" with computer "C" that runs Windows 7, the streamer reports many dropped frames. The support group told me that there are network issues, but they cannot help me.

UPDATE1 --------------------------------------

  • All network drivers are updated.
  • Computer "C" specs:
    • Processor Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz, 4001 Mhz, 4 Core(s), 8 Logical Processor(s)
    • Windows 7 Enterprise
    • Ram - 16G

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UPDATE2 --------------------------------------

This is the link to Wireshark's output.

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I'm trying to understand what is wrong with computer "C". I verified with iperf and ntttcp that I do have 10G bandwidth. I ran Wireshark on "C". According to Wireshark the tcp windows size drops to zero a lot. Probably this is the cause. Or one of the causes.

  1. What I can do in order to fix the tcp windows size? If you think this is not the problem, can you advise what should I check?
  2. Can tcp windows size problem be caused by how the streamer and reader handle the traffic? The way the reader handle the received buffers?
  3. Other reasons?
  • Are your drivers up to date? – Michael Hampton Aug 12 '16 at 22:59
  • 2.Can tcp windows size problem be caused by how the streamer and reader handle the traffic? The way the reader handle the received buffers? - The shrinking receive window has nothing to do with the sender and everything to do with the receiver. Are the Windows 7 drivers up to date? How much memory and CPU resources does the Windows 7 machine have? What do the memory, CPU, disk and network performance counters look like? – joeqwerty Aug 13 '16 at 0:24
  • @joeqwerty, I'v updated the post. What network performance counter you want? Please take a look. – theateist Aug 13 '16 at 2:09
  • If you are seeing zero window on Computer "C", then the application which accepts the stream is unable to process the data fast enough. Can you upload the capture file somewhere? – Mark Riddell Aug 13 '16 at 8:56
  • @MarkoPolo, a) But it does process the data fast enough in computer "B". b) I've uploaded the capture file. Please take a look at UPDATE2. – theateist Aug 13 '16 at 18:53
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If you have heavy stream between two computers you can use jumbo frames to reduce CPU load. If this technology was used on A and B computers you must enable it on the C computer. If computers aren't connected directly you must enable jumbo frames on network switches.

  • it's writen in my post that they are connected directly. The jumbo are also enabled. – theateist Aug 14 '16 at 6:57
  • Is the length of jumbo frames on both computers equal? – Mikhail Khirgiy Aug 14 '16 at 7:05
  • Yes, the length is 9K on both computers. – theateist Aug 14 '16 at 15:21
  • Does anyone have other suggestions? – theateist Aug 15 '16 at 4:59
  • Please, show models of both network adapters on B and C computers. Show result of command ping -f -l 8000 ip_a_computer on C computer. And show CPU, disk and network tabs from Resource Monitor when streamer and reader applications is running. Open Windows Task Manager, click the Performance tab and then the Resource Monitor button at the bottom. Alternatively type Resmon into Start or the Run box. – Mikhail Khirgiy Aug 17 '16 at 4:40

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